Upsample: A deviation from the original DRN model in our architecture, apart from model depth, is the use of a sub-pixel convolution layer[1]} for the upsampling of the final feature maps to create the ouput. The original DRN model uses either of bilinear upsampling or a deconvolution layer. In our model, sub-pixel convolution was chosen because it is faster for upsampling than standard deconvolution, while still having the advantage of learned upsampling. It performs a convolution in the low resolution space, and upsamples the result with a phase shift operation. Also, a sub-pixel convolution operation is mathematically equivalent to a deconvolution while still being faster.
